1. Field of the Invention
This invention is related to devices that conserve power and particularly to a circuit module that monitors the video signal and turns off power to the monitor when the monitor is not in use.
2. Prior Art and Information Disclosure
Various cirtcuits for conserving power have been disclosed which have general application.
For example, U.S. Pat. No. 4,970,408 to Hanke et al is for a CMOS power-on reset circuit whose output signal changes state upon detecting a predetermined threshhold of the power supply voltage during the startup transient then activates an inverter to substantially reduce the current through the power reset circuit to save power consumption.
U.S. Pat. No. 4,590,553 to Noda is for a microcomputer which is set to a power-save mode by an external signal and is provided with a flip-flop circuit for issuing a power save signal which is set when the microcomputer is set to a power save mode and reset upon receipt of a reset signal.
A number of devices are currently in or about to enter the market place for conserving power to computer circuits.
The "Monitor Miser" is a power saving module distributed by Technical Marketing partners in Mountain View, Calif. The Monitor Miser monitors keyboard activity and is connected between the keyboard and the CPU. When there is no activity for a user-specified period of time, Monitor Miser turns off the monitor. Then, when any key is touched, the monitor is turned back on.
"Powerkey" is a module produced by Sophisticated Circuits, Inc. Bothell, Wash. for the Macintosh. It is plugged into the Macintosh via an ADB port (Apple Desktop Bus). It has four outlet ports which turn on or off together under software control. The module can be programmed to turn the outlets on or off at preset times or by a phone call.
The Smartbar is a module produced by Sequence Electronics in Ontario Canada. The module has one connection to the keyboard and a second connection to a serial communications port. The Smartbar can be programmed to turn off after the keyboard has been inactive for a user-specified period of time. and can be instructed not to shut down if there are open files.
None of the devices available provide an inexpensive means for conserving power in response to detection of dormant periods where there is no video signal. Furthermore, the available power saving systems generally are constructed for use on specific brands of systems and require connection to ports of the system.